Methods of and apparatus for testing articles to determine to which of three groups the articles belong



Oct. 11, 1966 ERY, JR 3,278,849

INDICATOR D. EmE Q- .1

United States Patent M 3,278,849 METHODS OF AND APPARATUS FOR TESTING ARTICLES TO DETERMINE TO WHICH OF THREE GROUPS THE ARTICLES BELONG Loring D. Emery, Jr., Reading, Pa., assignor to Western Electric Company, Incorporated, New York, N.Y., a corporation of New York Filed Sept. 24, 1962, Ser. No. 225,543 5 Claims. (Cl. 324158) This invention relates to methods of and apparatus for testing articles and more particularly, to a method and apparatus for testing articles, such as semiconductor devices or the like, to determine to which of three groups the articles belong. Accordingly, the general objects of this invention are to provide new and improved methods and apparatus of such character.

These and other objects of the invention are accomplished by placing an article to be tested under test conditions to produce a reference signal representative of a characteristic of the article. The reference signal is then applied to a device, such as a relay, which will operate if the signal applied thereto is within a first range of values, will remain in an operated condition, once operated, if the signal applied thereto is within a second range of values, and will not operate if the signal applied thereto is within a third range of values. Accordingly, if the device operates when the reference signal is applied thereto, it indicates that the article characteristic has a value which is within the first range. If the device does not operate, it indicates that the article characteristic has a value which either lies within the second range or the third range. To determine within which of the latter two ranges the article characteristic lies, a signal is applied to the device having a value sufficient to cause operation thereof. The reference signal is then re-applied to the device and at the same time the operating signal is disconnected therefrom. If the device remains operated, it indicates that the article characteristic has a value which lies within the second range; if it fails to remain operated, it indicates that the article characteristic has a value which lies within the third range.

The invention will be more readily understood from the detailed description which follows when read in conjunction with the signal appended drawing which illustrates schemically an embodiment of the invention.

Referring now to the drawing, the apparatus illustrated therein includes a transistor, designated generally by the numeral 10, having a base 11, an emitter 12 and a collector 13. A relay 14 is connected to the emitter 12 and to ground. The relay 14 is a conventional electromechanical relay operable to energize upon one value of current passing therethrough and operable to stay energized upon the passage therethrough of a lesser value of current. Energization of the relay 14 closes a normally open contact 14a thereof, resulting in a circuit being established from a source of voltage 16 through the contact 14a to operate an indicating unit 18 which indicates the energization of the relay 14. The indicating unit 18 may be of a conventional form providing a visual, audible, or other type of indication.

The base 11 is connected to a terminal 19 adapted to receive one lead of an article to be tested. A second terminal 21 adapted to receive another lead of the article is connected to the collector 13 and to a source of adjustable DC. voltage 22. The function of the source 22 is twofold: first, it supplies the necessary bias to the transistor 10, and second, it provides a signal to the article to be tested. In parallel with the terminals 19 and 21 is a switch 23, operable upon closure to short out the article under test and thereby connect the base 11 directly to the voltage source 22.

3,278,849 Patented Oct. 11, 1966 a diode can fall according to its reverse current (I are as follows:

(1) Group IA reverse current (I greater than a predetermined value I (2) Group IIA reverse current (I between a predetermined value I, and I (I I I and (3) Group IIIA reverse current (I between zero and Prior to test, the apparatus is calibrated by adjustment of the source 22 so that the relay 14 energizes upon the passage therethrough of a value of current in excess of KI and stays energized, once energized, if the current therethrough exceeds a value K1 the factor K, in this instance, being the gain of the transistor 10 from the base 11 to the emitter 12. If the current is K1 or less, the relay 14 will not operate.

In operation, a diode 20 is inserted between the terminals 19 and 21 in its reverse direction, that is, its anode 24 is connected to terminal 21 and its cathode 25 is connected to terminal 19. The reverse current of the diode 20 is then amplified by transistor 10 and the amplified signal resulting therefrom is passed through the coil of the relay 14. If the relay 14 energizes, it means that the current therethrough must be greater than K1 and therefore the diode 20 belongs to Group I. However, if the relay 14 does not energize, it indicates that the diode 20 can either belong to Group II or to Group III. To determine in which of these two groups the diode 20 belongs, switch 23 is operated to its closed position. This shorts out the diode 20 and applies a large current to the base 11, which when amplified in the emitter circuit, energizes the relay 14. Upon opening of switch 23, if the diode 20 belongs to Group II, the current passing through relay 14 will be suflicient to keep the relay 14 energized; however, if the diode 2i) belongs to Group III, the amplified current will not be suiiicient to keep relay 14 energized and it will tie-energize.

It is to be understood that the above-described arrangement is simply illustrative of the application of the principles of the invention. Thus, although manual operation has been illustrated, it should be obvious to one skilled in the art that the apparatus is easily adaptable to automatic operation. Further, although the invention has been described and illustrated as being employed to test a semiconductor diode, according to its reverse current, it should be apparent that its use is not so limited and that the invention is readily adaptable to the testing of other articles, such as transistors, resistors, etc.

Numerous other arrangements may be readily devised by those skilled in the art which will embody the principles of the invention and fall within the spirit and scope thereof.

What is claimed is:

1. The method of testing a series of articles to determine to which one of three groups each of the articles belongs according to the value of a characteristic thereof, the characteristic being one which under test conditions is capable of varying the magnitude of an electrical reference signal as a function of the value of the characteristic, which method comprises:

(A) placing each article in turn under test conditions to produce a reference signal representative of the value of the characteristic;

(B) applying the reference signal to a sensing device of the type which operates initially only when the reference signal is above a first predetermined value corresponding to a first reference value of the charticle is known to belong to a third group whenever the device does not remain operated as a result of step (D).

(C) means for applying the reference Signal to the device,the device operating if the reference signal is greater than the first predetermined operating value of the device, thereby indicating that the artiacteristic under test, so that the article is known to cle characteristic has a value lying within a first belong to a first one of the three groups whenever range and that the article belongs to a first one of the device operates as a result of step (B); the groups; and r (C) momentarily applying a stronger signal to the (D) means selectively operable for momentarily apsensing device suflicient to insure that it operates ply g an Operating Signal to the deVlCe 1H mahtlef whenever the device does not operate in te (B); such that upon the removal of the operating signal and the reference signal is reapplied to the device, so that (D) applying the reference signal to the sensing device t the dEViCe does not p f p the lhltlal PP F while the device remains operated as a result of step r 0f the reference ga thereto, an operatlpg (C), the device being further of the type which re- 8 2 to Operate the tie/Vice 5 3 he momentarlly mains operated unless the reference signal is below a 15 PP thereto, thevdeYlce ffimalhlhg p t after second predetermined value lower than the first and the moment? Y aPphctttlofl 1f the reference signal has corresponding to a second reference value of the char- 3 vtthle greater than h f h Pfedetermlhed PP" acteristic under test, so that the article is known to beefatlhg of the device, lndtcatlhgthat the al'tlcle long to a second group whenever the device remains Characteflstlc has a Yahle lylhg Wlthln a Second operated a a lt f Step (1)) d so h h range and that the artlcle belongs to a second one of the groups, and the device being set to an unoperated condition if the reference signal has a value less than the second predetermined operating value, indicating that the article characteristic has a value lying within a third range and that the article belings to a third one of the groups.

4. Apparatus according to claim 3 wherein said device 2. The method of testing a series of articles to determine to which one of three groups each of the articles belongs according to the value of a resistance characteristic thereof, which method comprises:

(A) applying a signal to each article in turn to obis a ytain a responsive signal representative of the value of PP Q for testlhg a Sefles of articles to r th h t i i mum to which one of three groups each of the articles belongs according to the value of a resistance charac- (B) applying the responsive signal to a relay which teristlc thereof, which apparatus comprises:

energizes initially only when the responsive signal I is above a first predetermined value corresponding (A) first and second terminals for rece1ving an artito a first reference value of the resistance character- C16 to be tested;

istic under test, so that the article is known to belong (B) a voltage Squrce;

to a first one of the three groups whenever the relay a elay which energlzes 1n1t1ally when the s1gnal energizes as a result of Step (B); applied thereto is greater than a first predetermined (C) momentarily applying a Stronger Signal to the value and which remains energized, once energized,

relay sufiicient to insure that it energizes whenever as long as the sign a1 apphed thereto is greater than the relay does not energize in Step (B); and 4 a second predetermined value, less than the first; (D) applying the responsive Signal to the relay While (D) means for connecting the first and second termrthe relay remains energized as a result of Step (c), nals, the voltage source and the relay in a circuit the relay being further of the type which remains energized unless the responsive signal is below a such that (a) the signal applied to the relay is inversely proportional to the resistance across the second predetermined value lower than the first and first and sehond.terminals (b) the relay energizes corresponding to a Second reference Value of the when an artlcle 1s connected to the first and second Sistance characteristic under test so that the arr-isle terminals if the value of the resistance characteristic is known to belong to a Second group whenfiver the of the article lies within a first range of values, and relay remains energized as a result of step (D) and the relay remams.energlzed Once. hnerglzei so that the article is known to belong to a third 00 1f the value of the resistance characterlstic of the article lies within a second range; and

(E) a switch connected across the first and second terminals for selectively shorting and unshorting the terminals so that if the relay does not energize when the article is connected to the terminals, the terminals can first be shorted to increase the signal applied to the relay to energize the same and can then group whenever the relay does not remain energized as a result of step (D).

3. Apparatus for testing a series of articles to determine to which one of three groups each of the articles belongs according to the value of a characteristic thereof, the characteristic being one which under test conditions is capable of varying the magnitude of an electrical reference signal as a function of the value of the characterhe hhshoheh so that If the reslsthhce hhhrhhtehshc istic which apparatus comprises. of the article has a value lying within the second (A) means for placing an article to be tested unde range the hhhy Wih remain energized and if the test conditions to Produce a reference signal p? resistance characteristic of the article has a value resentative of the value of the characteristic under lylhg wlthlh h third range the relay Wlh dhhherglze' consideration- R f (B) a sensing device of the type which operates inie ehehchs Cheh by the Examiner tlally when the signal applied thereto is greater than UNITED STATES PATENTS a first predetermined value, and which remains operated, once operated, as long as the signal applied thereto is greater than a second predetermined value, less than the first;

2,958,823 11/1960 Rabier 324-133 WALTER L. CARLSON, Primary Examiner. E. L. STOLARUN, Assistanl Examiner. 

1. THE METHOD OF TESTING A SERIES OF ARTICLES TO DETERMINE TO WHICH ONE OF THREE GROUPS EACH OF THE ARTICLES BELONGS ACCORDING TO THE VALUE OF A CHARACTERISTIC THEREOF, THE CHARACTERISTIC BEING ONE WHICH UNDER TEST CONDITIONS IS CAPABLE OF VARYING THE MAGNITUDE OF AN ELECTRICAL REFERENCE SIGNAL AS A FUNCTION OF THE VALUE OF THE CHARACTERISTIC, WHICH METHOD COMPRISES: (A) PLACING EACH ARTICLE IN TURN UNDER TEST CONDITIONS TO PRODUCE A REFERENCE SIGNAL REPRESENTATIVE OF THE VALUE OF THE CHARACTERISTIC; (B) APPLYING THE REFERENCE SIGNAL TO A SENSING DEVICE OF THE TYPE WHICH OPERATES INITIALLY ONLY WHEN THE REFERENCE SIGNAL IS ABOVE A FIRST PREDETERMINED VALUE CORRESPONDING TO A FIRST REFERENCE VALUE OF THE CHARACTERISTIC UNDER TEST, SO THAT THE ARTICLE IS KNOWN TO BELONG TO A FIRST ONE OF THE THREE GROUPS WHENEVER THE DEVICE OPERATES AS A RESULT OF STEP (B); (C) MOMENTARILY APPLYING A STRONGER SIGNAL TO THE SENSING DEVICE SUFFICIENT TO INSURE THAT IT OPERATES WHENEVER THE DEVICE DOES NOT OPERATE IN STEP (B); AND (D) APPLYING THE REFERENCE SIGNAL TO THE SENSING DEVICE WHILE THE DEVICE REMAINS OPERATED AS A RESULT OF STEP (C), THE DEVICE BEING FURTHER OF THE TYPE WHICH REMAINS OPERATED UNLESS THE REFERENCE SIGNAL IS BELOW A SECOND PREDETERMINED VALUE LOWER THAN THE FIRST AND CORRESPONDING TO A SECOND REFERENCE VALUE OF THE CHARACTERISTIC UNDER TEST, SO THAT THE ARTICLE IS KNOWN TO BELONG TO A SECOND GROUP WHENEVER THE DEVICE REMAINS OPERATED AS A RESULT OF STEP (D) AND SO THAT THE ARTICLE IS KNOWN TO BELONG TO A THIRD GROUP WHENEVER THE DEVICE DOES NOT REMAIN OPERATED AS A RESULT OF STEP (D). 